1. Field of the Invention
This invention relates to the field of electrical connectors, and in particular to a current-mode coupler capable of non-invasively transferring electronic data signals to and from a twisted pair cable.
2. Description Of Related Art
Current-mode couplers are electrical connectors which enable sensing and transmission of low-level signal currents through an electrical conductor without an electrical connection to the conductor, thereby eliminating the need for direct wiring into the bus cable.
The present invention is an improvement on the current-mode coupler disclosed in U.S. Pat. No. 5,241,219, assigned to Amphenol Corporation, in which coupling to a twisted pair data bus cable is carried out by mating pairs of E-shaped electromagnets which surround the wires when the coupler is assembled to the data bus in order to establish an inductive coupling between the data bus and windings on the magnet cores, the windings being electrically connected to a control unit for sensing signals being transmitted along the data bus, and also for transmitting signals to the data bus.
The coupler assembly of U.S. Pat. No. 5,241,219 includes separate upper and lower metallic casing halves for housing the respective E-shaped magnetic cores. The cores are position relative to the data bus when the casing halves are latched together by means of a hook and slot arrangement at one end and a quarter turn latch at the other. Because of the unique design of the casing halves disclosed in U.S. Pat. No. 5,241,219, the assembly procedure can be carried out in extremely narrow spaces, while nevertheless permitting an exceptionally stable coupling.
Despite the numerous advantages of the current-mode coupler described in U.S. Pat. No. 5,241,219, the prior coupler design does have the disadvantage of less than optimal shielding resulting from the fact that the seam between the upper and lower casing, unless machined to a tolerance greater than is presently practical, incorporates relatively few points of electrical contact, and the points of contact are primarily butting rather than wiping points of contact, resulting in a relatively high impedance electrical connection between the conductive casing halves and an inadequate grounding of the casing half which is not otherwise secured to the structure on which the current-mode coupler is attached, for example a bulkhead in an aircraft.